A conventional hybrid vehicle includes a power distribution planetary gear mechanism having a sun gear, a carrier, and a ring gear to which a first motor/generator, an internal combustion engine, and a reduction mechanism that outputs power to a drive wheel are respectively connected, and a second motor/generator capable of outputting power to the ring gear of the planetary gear mechanism. A conventional control apparatus for this type of hybrid vehicle performs acceleration travel, in which the vehicle is accelerated by driving the vehicle using an output of the internal combustion engine, and inertial travel, in which the internal combustion engine is set in an inoperative condition such that the vehicle is caused to travel by inertia, alternately within a predetermined vehicle speed region. Further, in this type of conventional control apparatus, when the vehicle travels on a road surface having a downward gradient during the acceleration travel, the apparatus chooses either to maintain the acceleration travel or to switch to the inertial travel in order to reduce a fuel consumption rate, or in other words to increase a thermal efficiency of the internal combustion engine (see Patent Document 1). Patent Documents 2 to 4 are available as further related art documents relating to the invention.
Patent Document 1: Japanese Patent Application Publication No. 2010-280363 (JP 2010-280363 A)
Patent Document 2: Japanese Patent Application Publication No. 08-037702 (JP 08-037702 A)
Patent Document 3: Japanese Patent Application Publication No. 2002-095101 (JP 2002-095101 A)
Patent Document 4: Japanese Patent Application Publication No. 2009-274536 (JP 2009-274536 A)